Intel announced it will phase out the Core 2 Quad QX9770 and QX9650 processors in June 2009.
The last orders have to be placed shortly and as of end of Q2 2009 you wont be able to buy a Core 2 Extreme QX9770, at least not from Intel. The second CPU that faces retirement is Core 2 Extreme QX9650 and this 3.0GHz clocked and unlocked CPU also retires at the same time.
Intel wants you to buy Core i7 975 at 3.33GHz if you are top overclocker, or a Core i7 950 with 3.06GHz clock if you are after overclocking but be aware of the extra that you will need to spend for memory and expensive X58 board. The non-Extreme Core 2 Quad and the rest of 775 lineup will continue to live.